Karen, this is all the more reason why you should be using a table, rather
than columns. If you create a table with two columns and as many rows as you
have check boxes, you can place your check boxes in the first column and
enter your text in the second. You can size your first column so it's just
wide enough to hold your check boxes, and, if you want, you can take away
the table borders (Format > Borders and Shading) so no one even knows
there's a table there.
Use Tab and Shift+Tab to navigate the table cells.

Concerning your original question: To navigate in columns, first enter the
text in column one, then Insert > Break > Column Break > OK to break the
column and go to the top of the next one. Then type your way down that
column. Note that there are *no* keystrokes that take you back and forth
between columns. You have to click with the mouse to put the cursor in one
column or the other.